ARM: mach-shmobile: Runtime PM V3

This is the SH-Mobile ARM Runtime PM implementation V3.
Only clocks are managed at this point. If Runtime PM
is disabled then the clocks will be enabled before
->probe() and disabled after ->remove().

Signed-off-by: Magnus Damm <damm@opensource.se>
Signed-off-by: Paul Mundt <lethal@linux-sh.org>